Polymeric nonwoven webs formed by nonwoven extrusion processes such as, for example, meltblowing processes and spunbonding processes may be manufactured into products and components of products so inexpensively that the products could be viewed as disposable after only one or a few uses. Examples of such products include diapers, tissues, wipes, garments, mattress pads and feminine care products. There exists a continuing need for improved materials which are elastic, resilient, and flexible while still having a pleasing feel. A problem in fulfilling this need is that commercially viable elastic materials often feel rubbery.
The unpleasant tactile properties of elastic materials may be avoided by forming a laminate comprising an elastic sheet with one or more nonelastic sheets which have a soft feel. However, nonwoven webs formed from nonelastic polymers having improved tactile properties such as, for example, polypropylene are generally considered nonelastic. The lack of elasticity usually restricts these nonwoven fabrics to applications where elasticity is not required. Nevertheless, laminates of elastic and nonelastic materials have been made by bonding the nonelastic material to the elastic material in a manner that allows the laminate to stretch and recover yet which retains the desirable tactile properties of the nonelastic material. Elastic laminates, comprising an elastic sheet and a soft nonelastic material, are typically incorporated into products such that the soft material will contact a person's skin or forms the outermost portion of the product.
In one such laminate, a nonelastic material is joined to an elastic material while the elastic material is in a stretched condition so that when the elastic material is relaxed, the nonelastic material gathers between the locations where it is bonded to the elastic material. The resulting composite elastic material is readily stretchable to the extent that the nonelastic material gathered between the bond locations allows the elastic material to elongate. An example of this type of composite material is disclosed, for example, by U.S. Pat. No. 4,720,415 to Vander Wielen et al.
Another elastic laminate known in the art includes those conventionally referred to as "neck-bonded" materials. Necked-bonded materials are generally fabricated by bonding an elastic member to a non-elastic member while the non-elastic member is narrowed or necked. Neck-bonded laminates provide a material which is stretchable in the necked direction, the necked direction is most commonly also the cross-machine direction. Examples of neck-bonded laminates are described in commonly assigned U.S. Pat. Nos. 5,226,992 and 5,336,545 both to Morman. In addition, "reversibly necked materials" include materials which are stretchable to about the pre-necked dimensions and which, upon release of the stretching force, substantially recover to the necked dimensions unaided by additional materials. Such materials are typically formed by necking the material and treating the necked material, such as by heating and cooling the material, in order to impart memory of the necked dimensions to the material. Reversibly necked materials and methods of forming the same are disclosed in commonly assigned U.S. Pat. No. 4,965,122 to Morman.
Due to the methods of making elastic laminates, such as those described above, there exists a variety of elastic materials having the requisite characteristics for use in forming the elastic laminate structure. Similarly, there likewise exists a variety of neckable materials which are suitable for use in forming the elastic laminate structure. However, due to the variety of elastic and neckable materials potentially used to form elastic laminates there exist certain combinations of elastic and neckable materials which, although having excellent physical characteristics, do not adhere well to the other layers of the laminate. Thus, there exists a need for necked bonded laminates, and methods of producing the same, having improved integrity as well as the desired tactile and elastic properties.